I am trying to wire up my 450 dual viar compressors and was wondering if I could run a jumper wire to each relay. That way I wouldn’t have to run 2 wires back for the compressor power and 2 wires for the Pressure switch.
I mounted my relays under the hood and want to run as few wires back as possible. Can 2 relays be hooked up as one with jumper wires and not damage anything?
Can I combine the (2) 86 posts and run one wire back to the pressure switch and then combine the (2) 87 posts and run one wire back to the 2 Compressor Positive wires?
I am using 10 Gauge wire if that matters and it is about 8-10ft from relay to compressors.
Functionally it’ll work, but you have to be careful. If one relay fails for some reason, all the current will run through the other one. So, make sure to fuse each relay seperately coming from the battery. Viair says dual 450s draw 40 amps max so (2) 25 amp fuses would give you 50 amps worth of capacity. I would not put more than 50 amps of fuses on 10ft of 10ga. You can google wiring charts.
The wire coming from your pressure switch can easily trigger both relays. Mine triggers 4 relays.
You can combine the incoming lines as shown in my attached diagram. A word of extreme caution though - a lot of people don’t realize the damage a simple 12V solenoid can have on a car electrical system.
Inside the solenoid is a coil which acts like an electro magnet and pulls the contacts (i.e. the swtich part) closed as power if applied. When the trigger voltage to that coil get turned off, the coil electrical field collapses and the magnetic field is instantly converted back into electrical energy. This energy (spike) enters the vehicles electrical circuit and can reach voltages as high as 400V for a fraction of a second (easily enough to damage an ECU or other vital electronic component). I can upload a video of an example if you want - you need a logging multimeter to demonstrate it but it’s quite interesting to see how easily it happens.
It’s a big enough problem with single solenoid systems but I’m mentioning it especially here because with dual solenoids the chances of this occurring are multiplied and you really should take steps to avoid it.
Thankfully there’s a simple and cost effective solution to dealing with spikes like that - and it’s called a Transient Voltage Suppression diode (also known as a Transorb). Sure you can also use a Zener diode or a regular protection diode but the Transorb’s are the best protection in my book because of their speed and power rating. You wire the diode across the active trigger and then to ground. If a spike occurs, the diode will earth out the charge and prevent it from flowing back into your trigger circuit.
^^I wouldn’t either. It’s borderline. Heck, Air Zenith wants 6ga on their 35amp compressor.
DBO - Your diagram is like Viair’s - a single fuse before the dual relays. I think they show a 60amp fuse. Preeeettty sure they are 40amp relays. If one relay fails, you have the possibilty of sending 60amps through the other before the fuse pops. Especially since the OP wants a single wire running to his compressors. Not safe in my book. Each relay needs it’s own fuse with a lower rating than the relay.
Not so because the compressors are wired separately on the outbound side of the relay (i.e. one compressor per relay). If the relay fails, so does the corresponding compressor.
The scenario you describe would only happen if you link both compressors back up after the relays (i.e. joining the compressor power wires), which is something you don’t want to do for the exact reason you mentioned.
Thank you everyone for the wealth of info! Much to chew on but I think I will play it safe and run seperate wires for my power and for the pressure switch. Better safe than sorry!
I pointed it out because that’s exactly what he was asking about doing.
stickynicky: the trigger circuit through the pressure switch is very low current draw. We’re talking less than an amp. It’s no problem to run one wire for both relays & link them.
Thank you e2e! I got the wire ran and now can’t figure out which wire on the pressure switch I am supposed to hook up my key on wire. I am assuming that I hook up to the left hand side wire and that will give it power to kick on when the pressure is low enough. The right side wire goes to my relays. Is that correct?
Note: I put a toggle switch between my key on fused power wire that goes to the number 1 spot on my pressure switch. This is so I can turn the compressors off manually. Is this the correct way to do this?
Thank you guys so much for the help! It is making things much easier to understand and a lot safer too.
That sounds fine. Ultimately it doesn’t matter what switch wires you use since the switch sits in-line of a single wire. One side goes to your Accessory ON power (12V) and the other goes to the trigger pin on the relay.
Note: I put a toggle switch between my key on fused power wire that goes to the number 1 spot on my pressure switch. This is so I can turn the compressors off manually. Is this the correct way to do this?
Yes… all good.
Does it matter which wire I ground on the solenoid and which one I run to my factory horn wire?
No it doesn’t. Think of it in the same line as the pressure switch - that is… the solenoid is simply a switch and sits in-line of a power wire. One side goes to a supply voltage and the other goes to ground.
I will be using dual tanks on my system and was wondering if I should use a T to connect to tanks to the solenoid. Or should I just connect one of the tanks to the solenoid?
I will have a common line between the tanks to equalize them.
Normally if you join the tanks that’s all you’ll need. Not much point running dual air lines separately to the solenoid if all you do is merge them back down at that point - unless you’re running thinner line than the orifice in the solenoid.
What size line are you running and what kind of horns you got anyhow?
I got a S4 shocker kit that has sit unused for 3 years in my garage! I have the 1/2 Solenoid and the 5/16 lines. With dual 350c’s I think? I’m soooo close!
What size should I use between the tanks to equalize the air? I have a 2 gallon tank and a 2.5 Gallon tank.
I hope I can get a good few seconds of honk time with it.
The Shockers don’t suck that much air so you don’t need to be going with big barrel stuff everywhere. If the tanks have 1/2 ports then use that as the guide to bridge the tanks and up to the solenoid. I wouldn’t go smaller than what the max port size of your tank is. From the solenoid it’s fine to split via the banjo and then 5/16 to each horn. Keep the smaller lines running to the horns as short as possible and roughly the same length so they all sound at the same time.
With 4.5 gallons of air you’ll get plenty of honk time on the shockers.